Why is my if statement making the values of a previous array disappear?

Question

sasha 2014-6-17

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评论： Image Analyst 2014-6-17

My code basically looks like:

for x = 1:xmax
  for y = 1:ymax
    for l = 1:xmax
       for m = 1:ymax
          d(x,y,l,m) = (x-l)^2 + (y-m)^2
          if f(x,y,1) ~=f(x,y,5)
          %lots of new defined values
          else
             break
          end
       end
     end 
   end
end

There is no problem when I remove the if statement, I get the correct array for d. But when the if statement is there the output of d is all zeros. Does anyone know why d is not calculated when I have the conditional in there since it's outside of the if?

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Answer 1

A Jenkins 2014-6-17

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break will terminate your for loop, and it won't continue all the way to ymax.

Perhaps you mean you use continue? Or just leave the else case out altogether?

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sasha 2014-6-17

在 MATLAB Online 中打开

There was one more loop that I didn't put in that is in the code:

for t= 1:tmax
for x = 1:xmax
  for y = 1:ymax
    for l = 1:xmax
       for m = 1:ymax
          d(x,y,l,m) = (x-l)^2 + (y-m)^2
          if f(x,y,1) ~=f(x,y,5)
          %lots of new defined values
          else
             break
          end
       end
     end 
   end
end
end

I want the if statement to hold for all x and y and I want the time loop to be stopped if that condition is no longer true.

Is this the correct way to write it?

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Answer 2

Image Analyst 2014-6-17

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How would the f array ever change? And, have you tried stepping through the code with the debugger? That's what I do, and everyone else would do. Try this: http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/